Here's why Hugo Weaving didn't reprise his iconic role as Agent Smith in The Matrix Resurrections. After nearly 20 years, 2021 finally saw The Matrix franchise return, complete with co-creator Lana Wachowski back at the helm. While the resulting film has polarized both critics and fans, the reaction to it certainly isn't as harsh as that received by The Matrix Revolutions, so that in itself is perhaps a victory. In addition to Wachowski, Keanu Reeves and Carrie-Ann Moss returned to star as Neo and Trinity, respectively, despite their seeming death at the end of Revolutions.
Besides Neo and Trinity, several other notable characters came back from prior Matrix films for The Matrix Resurrections, mostly played by their original actors. Most notably, this included Jada Pinkett-Smith as an elderly version of Niobe, current leader of Io, The Matrix's human city that replaced Zion after Neo seemingly brought an end to the war between humans and machines. Unfortunately, two major returning characters were recast with new actors, those being Morpheus (with Yahya Abdul-Mateen II replacing Laurence Fishburne), and Agent Smith (with Jonathan Groff replacing Weaving).
This actually marks the second time Weaving didn't reprise a big role in a blockbuster franchise, as he declined to return as Red Skull in Avengers: Infinity War and Avengers: Endgame, after originating the part in Captain America: The First Avenger. While that case proved to be rather acrimonious, as Weaving disliked his experience working with Marvel, that's thankfully not the case for his failure to appear in The Matrix Resurrections. Instead, Weaving's absence comes down to a Hollywood staple: scheduling conflicts.
As Weaving told Collider in 2020, when it came time to make The Matrix Resurrections, director and co-writer Lana Wachowski very much wanted him to return as Agent Smith. After an initial bit of hesitation, Weaving agreed to do just that. However, the actor was busy doing a stage play at the time. The two sides entered into negotiations to try to make The Matrix Resurrections' schedule work out so that Weaving could do both projects, but, according to Weaving, Wachowski proved unwilling to accommodate the dates Weaving wanted.
Weaving doesn't appear to hold the decision against Wachowski on a personal level, but it's certainly disappointing that things ended the way they did. While Mindhunter's Groff does an excellent job trying to mimic aspects of Weaving's Agent Smith performance, seeing his Smith duke it out with Keanu Reeves' Neo just doesn't resonate the way a similar return bout between Weaving's Smith and Neo would have. Still, The Matrix Resurrections does setup a possible Matrix 5, so perhaps the original Weaving version of Smith could return for that. The nature of Smith as a renegade program within the matrix makes any potential future changes to his appearance easy to explain away.